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JSF binding conversion

Greenhorn

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posted 15 years ago

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Hi,

I use gmap4jsf to render some maps. I have something like this

<m:map latitude="#{city.latitude}"...

The problem is that the city latitude is a Double in my entity and gmap4jsf tag expects there a String.
Is there a nice way to convert the value to a string inside the EL expression?
The only solution that i found without changing the bean field type is adding a method
getLatitudeAsString in city object that returns the String converted value and then use "#{city.latitudeAsString}" in jsf.
Any ideeas?

Thanks

Tim Holloway

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posted 15 years ago

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Are you sure you're not making a problem where there isn't one? Since view definitions are in XML/HTML and only text (string) data is allowed in them, the EL processor automcatically handles string-to-xx and xx-to-string conversions.

The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.

You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.

Georgian Micsa

Greenhorn

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posted 15 years ago

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Well, in fact it seems that gmaps4jsf expects there a String:

java.lang.ClassCastException: java.lang.Double cannot be cast to java.lang.String
com.googlecode.gmaps4jsf.component.map.Map.getLatitude(Map.java:67)
com.googlecode.gmaps4jsf.util.MapRendererUtil.renderMapUsingLatLng(MapRendererUtil.java:121)
com.googlecode.gmaps4jsf.util.MapRendererUtil.startEncodingMapScript(MapRendererUtil.java:171)
com.googlecode.gmaps4jsf.component.map.MapRenderer.startEncodingMapRendererWrapper(MapRenderer.java:117)
com.googlecode.gmaps4jsf.component.map.MapRenderer.startEncodingMapWorld(MapRenderer.java:188)
com.googlecode.gmaps4jsf.component.map.MapRenderer.encodeBegin(MapRenderer.java:225)
javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:809)

The question remains open: is there a more elegant way to pass a String value to that tag without modifying my entity field.
I assume that the latitude and longitude fields must remain Double in my bean.

Thanks

Bauke Scholtz

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posted 15 years ago

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A double can in no way represent degrees, minutes and seconds. So I take the gmaps4jsf component for right.

Wrap your double getter by a string getter.

Tim Holloway

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posted 15 years ago

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I wrote my own Google Map JSF control a while back before all the other ones came out, so I went back and looked at the source code, since this sounds like a problem I had, but it appears that my map control did the conversions internally.

There's something odd going on here. The stack trace indicates a failure GETTING data from the map control, Since you didn't write the map control, I don't know how you could alter the data type it returns short of modifying the original source code. I'm still uncertain why the EL processor isn't handling the conversion here, but the first thing I'd do is check the TLD to make sure that an expression is even valid for that attribute. If only constants are allowed, that would cause a failure.

An example usage I found looks like this:

It's not using binary values, the latitude and longitude are decimal strings. But they're constants, not EL expressions.

I trust you're familiar with the author's web site at http://www.jroller.com/HazemBlog/entry/gmaps4jsf_create_your_map_with - he seems to have provided a rich set of examples.

Don't forget the GUnload(), BTW. Google maps leak when you do!

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